diff --git a/packages/react-resizable-panels-website/playwright.config.ts b/packages/react-resizable-panels-website/playwright.config.ts
index e72b6c69d..486245298 100644
--- a/packages/react-resizable-panels-website/playwright.config.ts
+++ b/packages/react-resizable-panels-website/playwright.config.ts
@@ -15,6 +15,7 @@ const config: PlaywrightTestConfig = {
     reuseExistingServer: true,
     url: "http://localhost:1234",
   },
+  timeout: 60_000,
 };
 
 if (process.env.DEBUG) {
@@ -23,7 +24,7 @@ if (process.env.DEBUG) {
     headless: false,
 
     launchOptions: {
-      slowMo: DEBUG ? 50 : undefined,
+      // slowMo: DEBUG ? 250 : undefined,
     },
   };
 }
diff --git a/packages/react-resizable-panels-website/src/routes/iframe/index.tsx b/packages/react-resizable-panels-website/src/routes/iframe/index.tsx
index 581186780..9abe3367b 100644
--- a/packages/react-resizable-panels-website/src/routes/iframe/index.tsx
+++ b/packages/react-resizable-panels-website/src/routes/iframe/index.tsx
@@ -1,23 +1,32 @@
-import { useState } from "react";
+import { useMemo, useSyncExternalStore } from "react";
 import styles from "./styles.module.css";
 
 export default function Page() {
-  const [url] = useState(() => {
-    const url = new URL(
-      typeof window !== undefined ? window.location.href : ""
-    );
+  const urlString = useSyncExternalStore(
+    function subscribe(onChange) {
+      window.addEventListener("navigate", onChange);
+      return function unsubscribe() {
+        window.removeEventListener("navigate", onChange);
+      };
+    },
+    function read() {
+      return window.location.href;
+    }
+  );
 
-    return `${url.origin}/__e2e/?urlPanelGroup=${url.searchParams.get(
-      "urlPanelGroup"
-    )}`;
-  });
+  const url = useMemo(() => new URL(urlString), [urlString]);
 
   return (
     <div className={styles.Root}>
       <iframe
         className={styles.IFrame}
-        sandbox="allow-scripts"
-        src={url}
+        id="frame"
+        sandbox={
+          url.searchParams.has("sameOrigin") ? undefined : "allow-scripts"
+        }
+        src={`${url.origin}/__e2e/?urlPanelGroup=${url.searchParams.get(
+          "urlPanelGroup"
+        )}`}
       ></iframe>
     </div>
   );
diff --git a/packages/react-resizable-panels-website/src/routes/iframe/styles.module.css b/packages/react-resizable-panels-website/src/routes/iframe/styles.module.css
index 8f79b8511..dff040e86 100644
--- a/packages/react-resizable-panels-website/src/routes/iframe/styles.module.css
+++ b/packages/react-resizable-panels-website/src/routes/iframe/styles.module.css
@@ -8,7 +8,7 @@
 }
 
 .IFrame {
-  width: 400px;
+  width: 300px;
   height: 200px;
   border: none;
 }
diff --git a/packages/react-resizable-panels-website/tests/ResizeHandle.spec.ts b/packages/react-resizable-panels-website/tests/ResizeHandle.spec.ts
index 75a56959a..dc13eded2 100644
--- a/packages/react-resizable-panels-website/tests/ResizeHandle.spec.ts
+++ b/packages/react-resizable-panels-website/tests/ResizeHandle.spec.ts
@@ -2,7 +2,8 @@ import { expect, test } from "@playwright/test";
 import { createElement } from "react";
 import { Panel, PanelGroup, PanelResizeHandle } from "react-resizable-panels";
 
-import { goToUrl } from "./utils/url";
+import { goToUrl, goToUrlWithIframe } from "./utils/url";
+import assert from "assert";
 
 test.describe("Resize handle", () => {
   test("should set 'data-resize-handle-active' attribute when active", async ({
@@ -14,9 +15,9 @@ test.describe("Resize handle", () => {
         PanelGroup,
         { direction: "horizontal" },
         createElement(Panel, { minSize: 10 }),
-        createElement(PanelResizeHandle, { style: { height: 10, width: 10 } }),
+        createElement(PanelResizeHandle),
         createElement(Panel, { minSize: 10 }),
-        createElement(PanelResizeHandle, { style: { height: 10, width: 10 } }),
+        createElement(PanelResizeHandle),
         createElement(Panel, { minSize: 10 })
       )
     );
@@ -70,4 +71,74 @@ test.describe("Resize handle", () => {
       await last.getAttribute("data-resize-handle-active")
     ).toBeNull();
   });
+
+  test("should stop dragging if the mouse is released outside of the document/owner", async ({
+    page,
+  }) => {
+    for (let sameOrigin of [true, false]) {
+      await goToUrlWithIframe(
+        page,
+        createElement(
+          PanelGroup,
+          { direction: "horizontal" },
+          createElement(Panel, { minSize: 10 }),
+          createElement(PanelResizeHandle),
+          createElement(Panel, { minSize: 10 })
+        ),
+        sameOrigin
+      );
+
+      const iframe = page.locator("iframe").first();
+      const iframeBounds = await iframe.boundingBox();
+      assert(iframeBounds);
+
+      const panel = page.frameLocator("#frame").locator("[data-panel]").first();
+      await expect(await panel.getAttribute("data-panel-size")).toBe("50.0");
+
+      const handle = page
+        .frameLocator("#frame")
+        .locator("[data-panel-resize-handle-id]")
+        .first();
+      const handleBounds = await handle.boundingBox();
+      assert(handleBounds);
+
+      // Mouse down
+      await page.mouse.move(handleBounds.x, handleBounds.y);
+      await page.mouse.down();
+
+      // Mouse move to iframe edge (and verify resize)
+      await page.mouse.move(iframeBounds.x, iframeBounds.y);
+      await expect(await panel.getAttribute("data-panel-size")).toBe("10.0");
+
+      // Mouse move outside of iframe (and verify no resize)
+      await page.mouse.move(iframeBounds.x - 10, iframeBounds.y - 10);
+      await expect(await panel.getAttribute("data-panel-size")).toBe("10.0");
+
+      // Mouse move within frame (and verify resize)
+      await page.mouse.move(iframeBounds.x, iframeBounds.y);
+      await page.mouse.move(handleBounds.x, handleBounds.y);
+      await expect(await panel.getAttribute("data-panel-size")).toBe("50.0");
+
+      // Mouse move to iframe edge
+      await page.mouse.move(
+        iframeBounds.x + iframeBounds.width,
+        iframeBounds.y + iframeBounds.height
+      );
+      await expect(await panel.getAttribute("data-panel-size")).toBe("90.0");
+
+      // Mouse move outside of iframe and release
+      await page.mouse.move(
+        iframeBounds.x + iframeBounds.width + 10,
+        iframeBounds.y + iframeBounds.height + 10
+      );
+      await expect(await panel.getAttribute("data-panel-size")).toBe("90.0");
+      await page.mouse.up();
+
+      // Mouse move within frame (and verify no resize)
+      await page.mouse.move(handleBounds.x, handleBounds.y);
+      await expect(await panel.getAttribute("data-panel-size")).toBe("90.0");
+      await page.mouse.move(iframeBounds.x, iframeBounds.y);
+      await expect(await panel.getAttribute("data-panel-size")).toBe("90.0");
+    }
+  });
 });
diff --git a/packages/react-resizable-panels-website/tests/StackingOrder.spec.ts b/packages/react-resizable-panels-website/tests/StackingOrder.spec.ts
index d6b560908..a369cfe9e 100644
--- a/packages/react-resizable-panels-website/tests/StackingOrder.spec.ts
+++ b/packages/react-resizable-panels-website/tests/StackingOrder.spec.ts
@@ -50,6 +50,8 @@ test.describe("stacking order", () => {
     const pageX = dragHandleRect.x + dragHandleRect.width / 2;
     const pageY = dragHandleRect.y + dragHandleRect.height / 2;
 
+    page.mouse.down();
+
     {
       page.mouse.move(pageX, pageY);
 
diff --git a/packages/react-resizable-panels-website/tests/utils/url.ts b/packages/react-resizable-panels-website/tests/utils/url.ts
index 8d5d237ba..18dcc4cf9 100644
--- a/packages/react-resizable-panels-website/tests/utils/url.ts
+++ b/packages/react-resizable-panels-website/tests/utils/url.ts
@@ -18,6 +18,25 @@ export async function goToUrl(
   await page.goto(url.toString());
 }
 
+export async function goToUrlWithIframe(
+  page: Page,
+  element: ReactElement<PanelGroupProps>,
+  sameOrigin: boolean
+) {
+  const encodedString = UrlPanelGroupToEncodedString(element);
+
+  const url = new URL("http://localhost:1234/__e2e/iframe");
+  url.searchParams.set("urlPanelGroup", encodedString);
+  if (sameOrigin) {
+    url.searchParams.set("sameOrigin", "");
+  }
+
+  // Uncomment when testing for easier repros
+  // console.log(url.toString());
+
+  await page.goto(url.toString());
+}
+
 export async function updateUrl(
   page: Page,
   element: ReactElement<PanelGroupProps> | null
diff --git a/packages/react-resizable-panels/src/PanelGroup.ts b/packages/react-resizable-panels/src/PanelGroup.ts
index 48c203b01..f9d4ac7f0 100644
--- a/packages/react-resizable-panels/src/PanelGroup.ts
+++ b/packages/react-resizable-panels/src/PanelGroup.ts
@@ -638,9 +638,6 @@ function PanelGroupWithForwardedRef({
         keyboardResizeBy,
         panelGroupElement
       );
-      if (delta === 0) {
-        return;
-      }
 
       // Support RTL layouts
       const isHorizontal = direction === "horizontal";
diff --git a/packages/react-resizable-panels/src/PanelResizeHandleRegistry.ts b/packages/react-resizable-panels/src/PanelResizeHandleRegistry.ts
index ae3068edf..f5844eb72 100644
--- a/packages/react-resizable-panels/src/PanelResizeHandleRegistry.ts
+++ b/packages/react-resizable-panels/src/PanelResizeHandleRegistry.ts
@@ -87,7 +87,7 @@ export function registerResizeHandle(
   };
 }
 
-function handlePointerDown(event: ResizeEvent) {
+function handlePointerDown(event: PointerEvent) {
   const { target } = event;
   const { x, y } = getResizeEventCoordinates(event);
 
@@ -104,9 +104,17 @@ function handlePointerDown(event: ResizeEvent) {
   }
 }
 
-function handlePointerMove(event: ResizeEvent) {
+function handlePointerMove(event: PointerEvent) {
   const { x, y } = getResizeEventCoordinates(event);
 
+  // Edge case (see #340)
+  // Detect when the pointer has been released outside an iframe on a different domain
+  if (event.buttons === 0) {
+    isPointerDown = false;
+
+    updateResizeHandlerStates("up", event);
+  }
+
   if (!isPointerDown) {
     const { target } = event;
 
diff --git a/packages/react-resizable-panels/src/hooks/useWindowSplitterBehavior.ts b/packages/react-resizable-panels/src/hooks/useWindowSplitterBehavior.ts
index 93383aaff..b0123bef9 100644
--- a/packages/react-resizable-panels/src/hooks/useWindowSplitterBehavior.ts
+++ b/packages/react-resizable-panels/src/hooks/useWindowSplitterBehavior.ts
@@ -71,8 +71,8 @@ export function useWindowSplitterResizeHandlerBehavior({
               ? index - 1
               : handles.length - 1
             : index + 1 < handles.length
-            ? index + 1
-            : 0;
+              ? index + 1
+              : 0;
 
           const nextHandle = handles[nextIndex] as HTMLElement;
           nextHandle.focus();
diff --git a/packages/react-resizable-panels/src/utils/test-utils.ts b/packages/react-resizable-panels/src/utils/test-utils.ts
index 0082084b8..faa87b985 100644
--- a/packages/react-resizable-panels/src/utils/test-utils.ts
+++ b/packages/react-resizable-panels/src/utils/test-utils.ts
@@ -12,6 +12,7 @@ export function dispatchPointerEvent(type: string, target: HTMLElement) {
     bubbles: true,
     clientX,
     clientY,
+    buttons: 1,
   });
   Object.defineProperties(event, {
     pageX: {
diff --git a/tsconfig.json b/tsconfig.json
index 195d7510a..4e1e9b8c8 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -9,8 +9,8 @@
     "noUncheckedIndexedAccess": true,
     "strict": true,
     "typeRoots": ["node_modules/@types"],
-    "types": ["jest", "node"]
+    "types": ["jest", "node"],
   },
   "exclude": ["node_modules"],
-  "include": ["declaration.d.ts", "packages/**/*.ts", "packages/**/*.tsx"]
+  "include": ["declaration.d.ts", "packages/**/*.ts", "packages/**/*.tsx"],
 }